s390: remove WARN_ON for misc_deregister() failures

The previous change added WARN_ON() in misc_deregister().  So it is not
necessary to WARN_ON() misc_deregister() failure by callers.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/s390/char/monreader.c b/drivers/s390/char/monreader.c
index 2ed3f82..e021ec6 100644
--- a/drivers/s390/char/monreader.c
+++ b/drivers/s390/char/monreader.c
@@ -627,7 +627,7 @@
 static void __exit mon_exit(void)
 {
 	segment_unload(mon_dcss_name);
-	WARN_ON(misc_deregister(&mon_dev) != 0);
+	misc_deregister(&mon_dev);
 	device_unregister(monreader_device);
 	driver_unregister(&monreader_driver);
 	iucv_unregister(&monreader_iucv_handler, 1);